英文:
How to create hashed index by mgo (golang)
问题
你可以使用mgo包来创建（或确保）哈希索引。以下是相当于你提供的代码的Go代码：
index := mgo.Index{
Key: []string{"hashed:_id"},
Background: true,
}
err := collection.EnsureIndex(index)
if err != nil {
// 处理错误
}
这段代码使用EnsureIndex方法来创建哈希索引。Key字段指定要创建索引的键，hashed:_id表示要对_id字段进行哈希索引。Background字段设置为true表示在后台创建索引。
请确保在使用此代码之前已经正确导入了mgo包，并且已经建立了与MongoDB的连接。
英文:
How can I create (or ensure) hashed index with mgo package?
I need a go code to be equivalent with this:
>> db.collection.createIndex( { _id: "hashed" } )
I have tried using runCommand but there is only createIndexes command that want a list of index specs. And I have no idea what is that and how I can create index specs.
答案1
得分: 3
你可以按照Collection.EnsureIndex中的文档进行操作：
> 通过该API还支持其他类型的索引。以下是一个示例：
index := Index{
Key: []string{"$2d:loc"},
Bits: 26,
}
err := collection.EnsureIndex(index)
> 上面的示例请求创建了一个针对"loc"字段的"2d"索引。
所以基本上，你可以使用以下格式：$<indexType>:<indexedField>，如下所示：
package main
import mgo "gopkg.in/mgo.v2"
const (
db = "so_hashed_idx"
coll = "testcoll"
)
func main() {
var s *mgo.Session
var err error
if s, err = mgo.Dial("127.0.0.1:27017"); err != nil {
panic(err)
}
// 索引规范只是一个花哨的词，用于将键或键/值对传递给Index类型的Key切片。
idx := mgo.Index{
Key: []string{"$hashed:_id"},
}
if err := s.DB(db).C(coll).EnsureIndex(idx); err != nil {
panic(err)
}
}
构建并运行上述代码将显示so_hashed_idx.testcoll的索引如下：
> db.testcoll.getIndices()
[
{
"v" : 1,
"key" : {
"_id" : 1
},
"name" : "_id_",
"ns" : "so_hashed_idx.testcoll"
},
{
"v" : 1,
"key" : {
"_id" : "hashed"
},
"name" : "_id_hashed",
"ns" : "so_hashed_idx.testcoll"
}
]
英文:
You can do it as documented at Collection.EnsureIndex:
> Other kinds of indexes are also supported through that API. Here is an example:
index := Index{
Key: []string{"$2d:loc"},
Bits: 26,
}
err := collection.EnsureIndex(index)
> The example above requests the creation of a "2d" index for the "loc" field.
So basically, you have the format $<indexType>:<indexedField>, as shown below:
package main
import mgo "gopkg.in/mgo.v2"
const (
db = "so_hashed_idx"
coll = "testcoll"
)
func main() {
var s *mgo.Session
var err error
if s, err = mgo.Dial("127.0.0.1:27017"); err != nil {
panic(err)
}
// An index spec is nothing more than a fancy word for the keys
// or the key/value pairs handed over to the Key slice of the
// Index type.
idx := mgo.Index{
Key: []string{"$hashed:_id"},
}
if err := s.DB(db).C(coll).EnsureIndex(idx); err != nil {
panic(err)
}
}
Building and running the above results in so_hashed_idx.testcoll showing its indices as follows
> db.testcoll.getIndices()
[
{
"v" : 1,
"key" : {
"_id" : 1
},
"name" : "_id_",
"ns" : "so_hashed_idx.testcoll"
},
{
"v" : 1,
"key" : {
"_id" : "hashed"
},
"name" : "_id_hashed",
"ns" : "so_hashed_idx.testcoll"
}
]
答案2
得分: 2
使用runCommand的答案：
func createHashedIndex(session *mgo.Session, collectionName string, indexKey string) {
var result interface{}
if err := session.Run(bson.D{
{"runCommand", collectionName},
{"command", []bson.M{bson.M{"name": indexKey+"_hashed_index", "key": bson.M{indexKey: "hashed"}}}}}, &result); err != nil {
fmt.Println("创建索引错误：", err.Error())
} else {
fmt.Println("创建索引：", result)
}
}
英文:
An answer with runCommand:
func createHashedIndex(session *mgo.Session, collectionName string, indexKey string){
var result interface{}
if err := session.Run(bson.D{
{"createIndexes", collectionName},
{"indexes", []bson.M{bson.M{"name": indexKey+"_hashed_index", "key": bson.M{indexKey: "hashed"}}}}}, &result); err != nil {
fmt.Println("Create Index Error:", err.Error())
} else {
fmt.Println("Create Index:", result)
}
}
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